REPRODUCTIONAsexual vs. Sexual

Asexual Reproduction

Asexual reproduction is the formation of new individuals from the cells of a single parent. It is very common in plants; less so in animals.

Or in the case of cells, asexual reproduction is making a new cell that is the same as the parent cell.

Asexual Reproduction in Plants—Stems!!!

All plant organs have been used for asexual reproduction, but stems are the most common.

In some species, stems arch over and take root at their tips, forming new plants.

The horizontal above-ground stems of the strawberry produce new daughter plants.

Asexual Reproduction in Plants—Leaves!!

This photo shows the leaves of the plant Bryophyllum. Mitosis along the leaf margins produces tiny plantlets that fall off and form new plants.

Asexual Reproduction in Plants—Roots!

Some plants use their roots for asexual reproduction.

The dandelion is a common example.

Trees, such as the poplar or aspen, send up new stems from their roots. In time, an entire grove of trees may form — all part of a clone of the original tree.

Asexual Reproduction in Plants—Plant propagation by people

Commercially-important plants are often deliberately propagated by asexual means in order to keep particularly desirable traits (e.g., flower color, flavor, resistance to disease).

Cuttings may be taken from the parent and rooted.

Grafting is widely used to propagate a desired variety of shrub or tree. All apple varieties, for example, are propagated this way.

Asexual Reproduction in Animals--Budding

In budding, offspring develop as a growth on the body of the parent.

In some species, e.g., jellyfishes and many echinoderms, the buds break away and take up an independent existence.

In others, like corals, the buds remain attached to the parent and the process results in colonies of animals.

Budding is also common among parasitic animals, e.g., tapeworms.

Asexual Reproduction in Animals--Parthenogenesis

In parthenogenesis ("virgin birth"), the females produce eggs, but these develop into young without ever being fertilized.

Parthenogenesis occurs in some fishes, several kinds of insects, and a few species of frogs and lizards.

Sharks!!!

Ants!!! I hate ants

Crayfish?

Lizards

Komodo Dragons!!!

So why don’t all organisms reproduce asexually?

You don’t have to waste all that time finding a mate.

And you get to pass on all of your own genes!!!

The advantages of Sexual reproduction

Sexual reproduction allows for greater diversity.

“Bad genes” can get covered up by good ones from the other parent.

Combinations of genes make it so organisms can better deal with changing environments.

So, now for cells and asexual reproduction.

The cell cycle asexually produces new body cells for:RepairReplacement Growth

The Cell Cycle

The cell cycle consists of three main parts.InterphaseMitosisCytokinesis

Interphase During

interphase, the cell is preparing to divide by making more organelles and copying its DNA.

Mitosis Mitosis is when the cell is

actually making the new cells. It consists of 4 steps or phases.ProphaseMetaphaseAnaphaseTelophase

Prophase During prophase, the

chromatin condenses into chromosomes.

Metaphase During metaphase,

chromosomes line up in the middle of the cell

Anaphase Anaphase is when the

chromosomes move to the opposite ends.

Telophase In telophase, the

chromosomes reach the opposite ends and the cell gets ready to actually split.

Cytokinesis During

cytokinesis, the cell divides into two cells.

Results of Mitosis Produces new body cells Cell copies DNA once Cell splits once 2 new (daughter) cells Daughter cells the same as the

parent cells Daughter cells have the same

number of chromosomes as the parent cells

Cells and Sexual Reproduction

A different type of cell must be produced for sexual reproduction.

These different cell are called sex cells, or gametesEgg = female gameteSperm = male gamete

Gametes!!! Since the gametes are going to

unite to make a new organism, each gamete only needs to have half the genetic information as its parent cell.

In mitosis, the cell copied its DNA once and split once.

In making sex cells, the cell has to copy it’s DNA once and then split twice.

Meiosis The process of making

gametes by copying the DNA once, and splitting twice is called meiosis.

Results of Meiosis Produces gametes (Sex cells) Cell copies DNA once Cell splits twice 4 new (daughter) cells Daughter cells different from parent

cells Daughter cells have the half the

number of chromosomes as the parent cells

Cell Division Comparison

MITOSIS MEIOSIS

Produces body cells Cell copies DNA once Cell splits once 2 new (daughter) cells New cells the same as

the parent cells Daughter cells have

the same number of chromosomes as the parent cells

Produces gametes Cell copies DNA once Cell splits twice 4 new (daughter) cells New cells different

from parent cells Daughter cells have

the half the number of chromosomes as the parent cells

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